Hélène VIVES – Growth of whiskers in Sn thin films on Cu-based substrates

Jury

Marc Verdier, Directeur de recherche, CNRS Alpes, Directeur de thèse
Damien Faurie, Professeur des Universités, Université Sorbonne Paris Nord, Rapporteur
Gregory Abadias, Professeur des Universités , Université de Poitiers, Rapporteur
Eric Chainet, Directeur de recherche, CNRS Alpes, Examinateur
Fabien Volpi, Professeur des Universités, Université Grenoble Alpes, Invité
Philippe Gendre, Docteur en science, AST PEM. AST pour Alberts Surface Technologies, Invité

Abstract

The ban on Pb in tin alloys for soldering has led to the formation of tin microfilaments, known as whiskers, on electrical connectors, which can cause short circuits. This thesis explores the growth mechanisms of these whiskers through microstructural studies, focusing on the application of tin by cold plastic deformation. Analysis of the microstructures and textures of Sn deposits reveals that a high copper content in the substrate favors the growth of InterMetallic Compounds (CIM) and extrusions, especially after accelerated ageing. Although CIM growth is not necessary for whisker formation, it facilitates nucleation and reduces incubation time, as do humidity and temperature. Tests reveal that whiskers form within the first 100 µm from the flat punch, contributing to a better understanding of the link between microstructure and Sn whisker formation.